Air conditioning apparatus



C. A. BULKEL'EY AIR CONDITIONING APPARATUS v July 16, 1940.

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Patented July l16, 1940 I l I UNITED.` STATES PATENT OFFICE 2,207,714 AIR CONDITIONINGAPPARATUS `Claude A. Bulkeley, New York, N. Y., assignor to Niagara Blower Company, New York, N. Y., a corporation of New York Application February 19, 1936, Serial No. 64,726

1o claims. (Cl. asv-3';

This invention relates to a method and ap- Fig. 1 is a'plan View of an enclosure and showparatus for conditioning air in and Ventilating an ing, diagrammatically, an air conditioning apenclosure and for cooling, heating, dehumidifying paratus and control system embodying my inand humidifying the air in the enclosure as condivention.

5 tions may require. The apparatus and control Fig. 2 is alongitudinal section through one of 5 can be used for so-called comfort air conditioning, the tubes of the cooling coils. l asin homes and theaters, where the primary ob- `In the following description it will be underjeci; is to maintain the air at the temperature and stood lthat the reference to thermostats and relative humidity most comfortable to the occuthermostatic control refers to a dry bulb thermopants and also for so-called industrial air condistat and to a control responsive to the dry bulb 10 vtioning where it is essential or desirable tomaintemperature in the enclosure, and that the terni tain, Within close limits, a definite relative huhygrostat designates an instrument which is remidity or a definite temperature, or both. SponSive tothe relative humidity in the enclosure.

'I'he principal object of this invention is to In its general organization this invention coml5 provide a simple control system for maintaining, prises means fOr drawing fresh air from the outl5 within a very close range, the'desired condition side and room air from the enclosure and passing of relative humidity and temperature within an it, counter now, over a multiple pass Cooling and enclosure consisting, essentially, of a hygrostat dehumidifying coil, the fresh air being directed controlling the temperature of the cooling me- 'against that part Of the COOlng C011 thrllgh zo dium and' a thermostat controlling the rate of which the cool water or other cooling medium 20 flow of 'the cooling medium. With a closed coil always passes when cooling and dehumidiflcation cooling system it has been found that this control iS being eieetedsSO that the greater Dart 0f the system will accurately maintain the desired concooling and dehumidiflcation is performed on the l-glition of' temperature and relative humidity in fresh air, together with means responsive to the the enclosure with a minimum expenditure of dry bulb temperature in the enClOSule fOr 00n- 25 refrigeration, trolling the rate of ow of the cooling medium Another object of the present invention is to through the coils and` means responsive t0 the provide such an air conditioning apparatus which relative humidity in the enclosure for controlling can be used for cooling and dehumidifying in the the temperature 0f the Cooling medium S0 aS to summertime and heating and humidifying in the maintain, Within Very C10Se limits. the temperaySi) Wintertime; in which the desired movement of ture and relative humidity desiredvwithin the enair in the enclosure is secured by recirculating Closure. Another feature of the invention conthe enclosure air through the apparatus and the SiStS in admitting the maximum amount of air desired amount of fresh air mixed with this-re'- from the air eOnditiOning apparatus to the encirculated air; in which the preponderance of the closure only When maximum heating 01' Cooling a5 cooling and dehumidifying is performed on the is desired and in cutting down the amount offresh air, the recirculated air being substantially air so admitted in response .to the enclosure temat the temperature and relative humidity desired; perature'as less heating or cooling is required. and in which the control system is simple and 'I'he numeral 5 represents an enclosure, such as inexpensive and is not liableto get out of order an auditorium or processing room, the. air of .and require adjustment. Whichis conditioned, under automatic control,

Another object is to include as a part of the by an air conditioning apparatus indicated gencontrol'system a thermostatic control of not only erally at 6. The air conditioning apparatus 6 the amount of cooling medium employed but also includes a casing l having a horizontal partition 45 the amount of air handled by the air condition- 8 forming an upper fresh air passage 9 and a 5 ing apparatus and admitted to the enclosure. To lower recirculated air-passage I0. In order to this end means are provided responsive to the secure the desired air movement in the room temperature in the enclosure for providing aand also to provide for ade uate cooling under maximum air delivery when maximum cooling heavy load conditions roo air 'is drawn out 0 or heating is required and for cutting down the through a duct Il into the passage I0 below the 5o air delivery when less cooling or heating is repartition 8. This room air ilows by a series ofquired until the point is reached where the minipasses of a serpentine cooling coil I2 through .mum required for ventilation and air movement which a cooling medium flows when cooling and lin the `enclosure is being supplied. dehumidincation is being performed `and then In the accompanying drawing; passes a series of sprays I3. which are operative v header 26.

when humidifying is performed and then passes through eliminator plates I4 which whip the air back and forth and remove any entrained moisture from the air. The air then passes around heating coils I5 into a fan inlet chamber I6 from which it passes into the inlet of a fan I1 which redelivers the air to the room 5 through a duct I3. 'I'he fresh air is drawn in through a fresh air inlet duct 20, past pre-heating coils 2| and through the passage 9 above the horizontal partition 8. The fresh air then flows by a series of passes of a serpentine cooling coil 22 and then past the humidifying sprays I3, eliminator plates I4, heating coil I5 and fan inlet chamber I6, mixing with the room air and being discharged into the room by the fan II through the duct I8.

The cooling coils I2 and 22 are conventially illustrated and a more detailed description of the construction of these cooling coils will be found in the prior Bulkeley Patents No. 2,001,704 dated May 21, 1935, and No. 2,006,344, dated July 2, 1935. Each of the cooling coils I2 and 22 consists of a plurality of serpentine tubes arranged one above the other and the corresponding ends of all of the tubes of the cooling coil I2 are con-V nected by an inlet header 23 and the opposite ends of the several tubes of this coil are connected with an outlet header 24. Similarly, the several serpentine tubes constituting the fresh air cooling coil 22 have their-corresponding ends connecting with an inlet header 25 and the other ends of these tubes are connected with an outlet It will be understood that each of the coils I2 and 22 can be sectionalized as shown in the said Patent No. 2,001,704. It can be observed that the flow of the refrigerating medium through the cooling coils I2 and 22 is in the opposite direction from the air flow. It will also be observed that the tubes constituting the fresh air coil 22 are longer and include more passes than the tubes constituting the recirculated air coil I2 for the purpose set forth in the said prior Patent No. 2,001,704.l The refrigerating medium is admitted to the coils I2 and 22 at a temperature below the dewpoint of the passing air so that that part of the passing air coming in contact with the final pass or passes of each coil is chilled below its dewpoint and moisture is precipitated out of the air so as to secure dehumidication as well as cooling. Only a very short section at the end of the coil from which the air leaves is required to b'e cooled below the dewpoint of the air in order to effect the necessary dehumidication.

It has been found that the rate of ow of the influence on the dehumidifying effect of the coils.

On the other hand, the entering temperature of the cooling medium 4determines the dehumidifying effect of the coils as well as the cooling effect thereof providing, of course, this temperature is appreciably below the dewpoint of the air. It will therefore be seen that a very simple control for maintaining, within very close limits, the desired relative humidity and temperature in the enclosure 5 vcan be achieved by the simple expedient of controlling the rate of ow of refrigerant through the coils in response to the dry bulb temperature of the air in the room and by control- 4 ling the entering temperature of the cooling medium entering the cooling coils in response to the relative humidity of the air within the enclosure. By this means if the temperature in the room rises the flow of cooling medium through the coils is increased without substantially increasing the dehumidifying effect of the coils. If the relative humidity in the room rises labove the setting of the hygrostat it will operate to decrease the initial temperature of the cooling medium, thereby increasing the dehumidifying effect of the cooling coils without greatly increasing the cooling eect. It will be seen that by thermostatically controlling that condition of the cooling medium in a cooling coil which most largely iniiuences the cooling effect of the coil in removing sensible heat and hydrostatically controlling that condition of the cooling medium in the cooling coil which most largely influences the dehumidifying effect in the removal of latent heat, an economy in refrigeration is effected since useless cooling of the air is not doneto secure the desired dehumidification and useless dehumidiflcation of the air is not done to secure the desired cooling of the air.

pressure to both of the coils from a supply pipe 30. This cooling medium can be in the form of brine br cold water and is preferably supplied at a constant temperature o-f such low degree as to permit of lowering the dewpoint of the air passing the cooling coils to the minimum degree desired. The cooling medium is also available in such quantity as to take care. of the maximum heat load imposed upon the apparatus. It will also 'be understood that the cooling water can be supplied from any suitable natural or artificial source and that any other form of cooling medium can be used, such as a liquid refrigerant expanded directly in the cooling coils, the entering temperature of such direct expanded cooling medium and the mean temperature of the coils being suitably controlled for this purpose.

The cooling medium from the supply pipe 30 can pass through a branch .pipe 3I to the inlet header 25 of the fresh air cooling coil 22. The cooling medium. so supplied iiows through the cooling coil 22 counter to the fresh air flow and into the outlet header 26. From the outlet header the cooling medium is withdrawn through a pipe 32, by a pump 33, the outlet of which is connected by a pipe 34 with the branch pipe 3| leading to the inlet header of the fresh air cooling coil. The pump 33 is driven by an electric motor 35.

Similarly, the cooling medium is supplied to the recirculated air cooling coils from the supply pipe 30 by a branch pipe 36 which connects with the inlet header 23 of the recirculated air coils I2. The outlet header 24 of the recirculated air cooling coils is connected by a pipe 31 with the inlet of a pump 38 driven by an electric motor 39. The outlet pipe 40 of the pump 38 connects with the branch pipe 36 leading to the inlet header 23 of the recirculated air cooling coils I2. That part of the cooling medium not recirculated by the pumps 33 and 38 is returned to the refrigerating apparatus (not shown) by a common return pipe 4I, one branch 42 of which connects with a three-way diaphragm valve 43 located in the return pipe 32 between the fresh air outlet header 26 and the recirculation pump 33. The other branch 44 of the common refrigerating medium return pipe 4I connects with a three-way diaphragm valve 45 located in the return pipe 31 between the outlet header 24 of the recirculation air cooling coil I2 and the recirculating pump 38. f

,The amount of cooling medium admitted to the fresh air coil 22 is controlled by a reverse acting diaphragm valve and a by-pass 5I is provided around this valve having a manually operable. valve 52, the opening of which permits a minimum amount of cooling medium to be admitted to the fresh aircoil 22 when the diaphragm valve 50 is completely closed. Similarly, a reverse acting diaphragm valve 53 regulates the amount of cooling medium admitted to the recirculated air coil I2, a by-pass pipe'54 being provided around this diaphragm valve 53 and including a hand operated valve 55 which,

,when opened, provides a minimum flow of cooling medium through the recirculated air coil I2. The reverse acting valves 50 and 53 are so adjusted that the diaphragm valve 50 opens in advance of the diaphragm valve 53 so that under all conditions of cooling the fresh air cooling coil 22 is operative and the recirculated air cooling coil I2 is only operative under heavier load conditions. Conversely, of course, the diaphragm valve 53 closes in advance of the diaphragm valve 50 so as to cut out the recirculated air coil I2' first as the load on the apparatus is relieved.

As previously stated the rate of flow of the cooling medium through the fresh air coil 22 and the rate of flow through both the fresh air coil 22 and the recirculated air coil I2 'is adjusted in accordance with the dry bulb temperature of the room 5 so as to secure the desired cooling of the air in the room. For this purpose a direct acting dry bulb thermostat is shown as being located in the room 5 and as having its sensitive parts exposed to the airA in this room, although it will be understood that this thermostat could be located in the return air passage I I or that room a`ir could be brought to the sensitive parts of the thermostat if it were desired to locate the thermostat on a remote instrument panel. The thermostat $0 is of the direct acting pneumatic type and is supplied with air pressure at, say 15 pounds, from an air pressure line 5I The outlet line 62 connects directly with both of the reverse acting diaphragm valves 50 and 53 so that upon rising room temperature the pressure in the thermostat outlet line rises and progressively opens the diaphragm valves 5I! and 53 so as to admit increasing amounts of cooling medium first to the fresh air coil 22 until the full rate of now of the cooling medium obtains through this coil and then to the recirculated air coil I2 until the full rate of ow obtains in this coil, under whichl condition the apparatus is operating under maximum load'conditions.

As previously stated the temperature of th cooling medium admitted tb the-coils I2 and 22 is under hygrostat control and for this purpose a reverse acting hygrostat is'lo'cated in the room 5 and is of the pneumatic type, being supplied with air pressure from the main pressure supply line 6l. It will beunderstood that, as with the thermostat 60, the sensitive parts of the hygrostat can be located in the recirculated air duct II or that enclosure air can be brought to these sensitive parts if it is convenient to locate the hygrostat on a remote instrument board. The outlet line 65 from the reverse acting hygrostat 55 connects with a thermostat 61 having its sensitive parts located in the cooling medium supply branch 3l to the iresh air coil 22 and also connects withv asimilar thermostat 68 having its sensitive parts in the cooling medium supply branch 36 to the recirculated air coil I2. L The outlet line 89 from the thermostat 61 connects directly with the tlnee-way diaphragm valve 43 in the refrigerating medium return pipe 32 and the outlet line 10 from the thermostat B8 connects directly with the three-way diaphragml valve 45 in the refrigerating medium return pipe 31 from the recirculated air coil I2. 'I'he purpose of the thermostats 61 and 68 is to prevent the hygrostat 65 from raising the entering cooling medium temperature above that required to stop dehumidiication and at all times maintain the maximum inlet water temperature low enough to cool the air the required amount.

fio

I2 it will be understood thatrth'e pumps 33 and 38 serve to dilute the cooling medium supplied to the. cooling coils with relatively Warm return' or spent cooling medium from these coils. The three-Way diaphragm valves 43 and 45 serve to permit a greater or less amount of the return water from the coils to be so directly returned to the inlet branches of the cooling coils and therefore these three-way diaphragm valves operate to control the temperature of the water admitted to the coils. As the relative humidity in the room 5 rises, the pressure in the outlet line 65 from the reverse acting hygrostat B5 drops and this pressure drop is transmitted through the thermostats 61 and 68 to function the threeway diaphragm valves 43 and 45 to cut down the amount of cooling medium admitted, respectively. to the pumps 33 and 38 and increase the amount of cooling medium returned through the common pipe 4I to the refrigerating apparatus (not shown). This, of course, cuts down the dilution of the incoming cooling medium to the coils I2 and 22 by the spent cooling medium and hence lowers the temperature of the cooling medium admitted to the coils.l Both of the pumps 33 and 38 are kept running as long as dehumidification or cooling is required.

In order to reduce the amount of refrigeration required in the summertime and also to reduce the heating required in the wintertime means are provided for reducing the amount of air handled by the air conditioningapparatus when the load in the room is decreased and less heating or cooling andventilation is required. This means is functioned by the 'direct acting thermostat 60 and since the conditions are exactly reversed, ofcourse, when heating, as compared with cooling, it will be seen that a reversal in the action of the thermostat must take place. To this end the various diaphragm valves ineluded in the system operate within certainair pressure ranges which, for convenience, will be stat El) is connected with a snap .relay 18 and.

the outlet line 19 of this snap relay is in turn connected with athree-way diaphragm valve 80.

vThis three-way ldiaphragm valve has one' inlet connection with the outlet line 62 from the direct acting thermostat 68 and its outlet is connected by a line 8l with the damper motor 16. During summer operation when cooling is required, the outlet pressure of the direct acting thermostat is'such as to cause the snap relay 18 to disnear nect its outlet line I9 from the main pressure supply line 6| under which condition no pressure is impressed upon the diaphragm of the valve and its outlet line 8| is connected with the thermostat outlet line 62 so that the air motor 16 is under direct control of the direct acting thermostat 60. Consequently, as the room temperature falls toward the setting of the direct acting thermostat 60 the outlet pressure in its outlet line 62 and also in the damper motor line 8| likewise drops, causing the damper motor to close the dampers proportionately. Of course, when the temperature in the room 5 reaches the setting of the thermostat no cooling is required and consequently at this point the dampers 'I5 are 'outlet line 8| with a line 85 which is the outlet line from a reverse acting rfelay 86. The outlet line 62 from the direct acting thermostat 60 convnects with and functions this reverse acting relay 86 and it is supplied with air pressure from. the main pressure supply line 6| for its operation. Thus, in the wintertime when heating is required the action of the thermostat 60 on the dampers 15 is reversed by the reverse acting relay *.6 so that as the temperature in the room 5 rises to the setting of the thermostat 60, the4 rising pressure in its outlet line 62 causes a falling pressure in the outlet line to the reverse acting relay 86 and this progressively closes the dampers I5 until they are half way closed, l. e. their maximum extent, when' the temperature of the room reaches the setting of the thermostat.

For winter operation the outlet line 62 from the thermostat 60 connects with a direct acting .diaphragm valve 81 which inconjunction with the .iermostat 60 admits more steam from a steam supply line to the heater I5 as the room temperature drops. Also during winter operation the hygrostat 56 functions a reverse acting diaphragm valve 88 which admits water from a line 89 to the sprays I3 so as to humidify the air ad'- mitted to the enclosure until the setting of the hygrostat is reached.

It is also desirable to place a barrier or baffle means in the tubes of the cooling coil which preferably impose a minimum restriction to .the flow of lthe refrigerant but serve to create a turbulence in the flowing refrigerant even at 4extremely low rates of flow thereof. By so maintaining a turbulent condition at very low rates of flow, a high transfer rate is maintained between the liquid refrigerant and the cooling surface or tubes. Any suitable vmeans such as a twisted ribbon or spiral wire (not shown) in the tubes of the cooling coil will do. The purpose of this ribbon is to maintain a. high rate of heat transfer, commonly known as K value, when dehumid-r ification is required with a minimum removal of coils as the bubbles formed by the expansion maintain the necessary turbulence even at low rates of ow of the refrigerant. f

Operation air so that an excessive pressure is not built up in the enclosure. At the same time a refrigerating medium, such as brine, from the cooler (not shown) of a conventional refrigerating apparatus is supplied under pressure and preferably `at a constant temperature from the pipe 30 through the two branches 3| and 36 leading to the inlet headers 25 and 23 of the fresh air cooling coil 22 and recirculated air cooling coil I2, respectively. In these cooling coils the air flows counter-current tov the refrigerant iiow so that in passing the several passes of each coil the air is progressively cooled and upon reaching the last or coldest pass, that portion of the air actually coming in contact with this passlwill be dehurnidifled. The air, however, leaves the coils at a tem-f perature substantially above its dewpoint. The

fresh air cooling coil 22 is much longer in the direction of air flow than the recirculated air coil inasmuch as the greater cooling is performed `on the fresh air which is generally more moist yand humid than the recirculated air, the recirculated air being, of course, substantially at the temperature and relative humidity desired. -For this reason the fresh airv cooling coil 22 is lalso always operative as long as cooling is to be performed and the cooling medium is admitted in substantial quantities to the recirculated air cooling coil only when th'e Aheat load inthe room, rises above thec'apacity ofthe fresh air cooling coil.'

The essence of the present invention resides in the control ofthe rate of flow of the coolingl medium through the coils in response tothe ldry bulb temperature of 'the vroom and the vcontrol of the entering temperature of 'the refrigerating medium to the coils in response to the relative humidity in the room. It has been found that when the rate of Aflow of a cooling medium of constant temperature is increased, the cooling effect of the coil, i. e." its effect in removing s e'n'- ire water to do the same amount of cooling're'- sults in lower mean temperatureI of the water flowingthrough the coil. However, the increase in the -fiow of the cooling medium has a relatively slight ifect uponzthe dehmidlfylng action of the coil in removing latent heat. occurs because cooling of the air will always occur if the water is at a lower temperature than the air. However, no dehumidifyin'g of the 'air can occur unless the initial or entering temperature of the water is appreciably lower (3'5 F.) 'than Greater cooling cool enough to do the necessary cooling. When the entering temperature of the cooling medium is below the dewpoint of the air so that dehumidiflcation takes place, an increase in the rate of flow has a relatively slight effect upon the dehumidifying action of the coil. Accordingly, it will be seen that a thermostat control of the rate of flow will provide the desired dry bulb temperature in the room but will have little effect in adjusting the removal of moisture and will have no effect at all if the initial temperature of the cooling medium is too high to effect condensation.

As the air passes through the cooling coils it is progressively cooled by the colder and colder passes so that when it reaches the end of the coll it is near its dewpoint. If the entering temperature of the cooling medium is appreciably below l the dewpoint of the air, that portion of the precooled air which strikes the final pass or passesA of the cooling coil will be chilled below its dewpoint so that dehumidiflcation takes place. The amount of this dehumidiflcation is directly dependent upon the entering temperature of the cooling medium and hence by adjusting this entering temperature in accordance with the relative humidity in the room it will be seen that an exact control of the relative humidity can be obtained. Of course, decreasing the temperature of the entering cooling medium tends to decrease the 'mean temperature difference between the cooling coil and the air so that more sensible heat would be removed. However, if this cooling is excessive it will be seen that the thermostat in the enclosure will cut down the rate of flow so that the coil will remove sensible heat only to the extent required.

It will therefore be seen that by such a system an extremely accurate control of both the relative humidity and the temperature in the room can be obtained, a condition which is particularly important in processing moisture or heat sensitive materials. Further, it will be seen that there is a saving in refrigerant since at no time is useless dehumidification performed in order to bring down the dry bulb temperature of the room, nor is there useless removal of sensible heat in order to secure dehumidication. It will be appreciated that this is particularly important as many sysg.

livers rising air pressure to line B2 which will deliver air at relatively high pressure (12 or 13 pounds) so as to hold the reverse acting valves 50 and 53 wide open, allowing the maximum volume of cooling medium tofiow through both the fresh air coil 22 and the recirculated air coil l2, thereby to provide the maximum cooling of the passing air at the particular entering temperature of the cooling medium then being maintainedl by the hygrostat 65. As the room temperature falls the thermostat causes the pressure in its outlet line 82 to drop first closing the valve 53 so as to reduce the flow of refrigerating medium through the branch pipe 28 and recirculation air coil I2 and then closing the valve 50 so as to reduce the flow of cooling medium through the branch pipe 3| and fresh air coll 22. These valves 50 and 53 may overlap in operation but essentially the valves 50 and 53 are completely functioned at a control air pressure in line 62 of between 12 and 8 pounds. Each of these valves is provided with a hand controlled valved by-pass 52 and 55 to allow a desired minimum flow of Water for effecting dehumidication by the fresh and recirculated air cooling coils when the valves 50 and 53 are completely closed by the thermostat 80.

At controlling air pressures above '7.5 pounds in the outlet line 52 from the thermostat 6U the snap relay 18 is held in' the position in which it admits full air pressure from the main air pressure supply line (ilV to the diaphragm valve 80 so that the diaphragm valve- 80 connects the diaphragm motor 16 with the thermostat outlet line B2. Therefore, the drop in pressure in the thermostat outlet line 62 due to falling room temperature caused by increased cooling and approaching that which the thermostat is desired to maintain' actuates the motor 16 to gradually close the damper 15 until the stop l1 is encountered.

This closing'of the dempers 15 occurs with falll valves 50 and 53. It will therefore be seen that duringk cooling operation as the heat load inthe room drops and less cooling is required,k the amount of air delivered to the room is also reduced. It will be appreciated that in order to accomplish cooling a sufficient volume or weight of alr must be treated so that this airdelivered into the enclosure will absorb the maximum heat load at a predetermined maximum differential temperature between the room air and the incoming air as it is n ot advisable, for` reasons of comfort, to deliver air at too cold a temperature. It therefore follows that at any time when the heat load is less than maximum, either the temperature diiferential between the incoming air and the room air, or the Volume or weight of air admitted to the enclosure, can be reduced in proportion or both the temperature diiferential and the volume can be reduced. Assuming that the maximum allowable temperature differential between the incoming air and the enclosure air be 15, such as with a room temperature of '75 F. /land airv delivered to the room at 60-'F. and that 1000 pounds per minute of air must be delivered to absorb the maximum heat load which would be 3600 B. t. u. per minute it will be seen that if the heat load /is reduced to one-half or 1800r B. t. u. per minute, then in order to maintain the room temperature constant the differential tem- 4 perature between the incoming and room air must be reduced to 7.5 or any combination of the two that will glvea common product which will equal the heat load.

It will be seen that the present invention provides maximum air volume when maximum cooling is required. Were it not for the requirements of ventilation and air movement in the enclosure no air would need to be handled if no cooling were required. In practice it has been found that under light load conditions a reduction to approximately one-half the maximum air volume can be safely used when minimum cooling or heating is required and at the same time maintain I satisfactory air conditions.

The entire operation as above described, is, of course, reversed on rising room temperatures.

Assuming that the air in the enclosure has too high a relative humidity, since the hygrostat 65 is reverse acting and gives falling air pressure to its outlet 66 with rising relative humidity the pressure in its outlet line 66 and in the lines 69 and to the three-way valves 43 and 45 will be low, andl hence the cooling medium will all be returned through the common pipe 4| to be re-cooled by the refrigerating apparatus (not shown). Under this condition the cooling medium is supplied to the fresh and recirculated air cooling coils at minimum temperature from the'refrigerating medium supply line, thus accomplishing the maximum amount of dehumidification of both fresh and recirculated air. The pumps 33 and 38 are kept running whenever cooling or dehumidifying is required and as the relative humidity falls the pressure in lines 66, 68 and 10 rises from 2 to 7 pounds, in which range of rising pressure and falling relative humidity the three-way valve 45 first functions to direct an increasing flow of spent cooling medium through the recirculation pump 38 to the inlet branch 36, of the recirculated air coil I2, thereb;7 diluting the cooling medium admitted to this coil and causing the temperature of the cooling medium entering this coil to rise and thereafter to do likewise with the three-way valve 43, causing this valve to divert increasing amounts of spent water through the pump 33 so as to dilute the cooling medium admitted to the fresh air coil and raise the entering temperature of the water in the fresh air coil. This increase in the entering temperature of the cooling medium admitted to the fresh and recirculated air cooling coils reduces the amount of dehumidifying performed by these coils. These three-way diaphragm valves 43 and 45 may overlap in this operation but with falling relative humidity the valve 43 in the fresh air cooling medium system will function after the three-way valve 45 in the recirculated air system to increase the dilution of the refrigerating medium since more dehumidication of fresh air is likely to be required when cooling is needed.

The thermostats 61 and 68 are set to maintain a maximum temperature to which the hygrostat 65 may raise the entering temperature of the cooling medium to the coils. This temperature Which these thermostats are set to maintain should be about 3 or 4 below the desired dewpoint temperature required in the room. 'Ihis is to prevent the hygrostat from raising the entering cooling medium temperature above that required to stop dehumidication so that the entering Water temperature is still low enough to cool the air the required amount. In acting to prevent the entering temperature of the cooling medium from rising above this predetermined minimum each of these limiting thermostats 67 and 68 throttle the air pressure to the respective three-way diaphragm valves 33 and 45 so that these valves cannot function to increase the entering temperature of the cooling medium beyond from 3 to 4 below the dewpoint of the air handled.

- Thus, if the weather is very hot but very dry the fresh air admitted in the enclosure 5 lowers its relative humidity. This, of course, raises the pressure in the hygrostat outlet line 66 until the diaphgram valves 43 and 45 are functioned to return the maximum amount of spent cooling Water to the 'pumps 35 and 39 which return this water directly to the inlet branch pipes of the cooling coils. If all the water to the coils were permittedto be recirculated it will be seen that no cooling would take place and consequently the temperature in the room 5 would rise to the outside temperature or higher. To avoid this the thermostats 61 and 68 insure that the diaphragm valves 43 and 45 can never completely cut off the refrigerating medium from the pipe 30 and insure that the temperature of the entering cooling medium can never rise above a temperature of 3 or 4 below the dewpoint of the air in the enclosure so that cooling will be done even though dehumidification is not required. l

. Under the condition just assumed, that is, extremely hot and dry Weather, the relative humidity in the room will fall, thereby functioning the reverse acting hygrostat 65 to raise the pressure in its outlet line 66. When this pressure rises to 8 pounds the reverse acting diaphragm valve 88 commences to open so as to admit water to the humidifying sprays I3 and thereby humidify the air. admitted to the room 5 and maintain the desired relative humidity therein. The diaphragm valve 88 is moved from its completely off to its maximum open positions under pressures in the hygrostat outlet line of from 8 to 13 pounds.

On the other hand if the outside conditions are such that the air is cool and moist the fall in temperature in the enclosure 8 will rst function the direct acting thermostat 60 to cause a drop in pressure in its outlet line 62. When this pressure drops to 8 pounds both of the diaphragm valves 58 and 53 are completely closed, the diaphragm valve 58 controlling the admission of cooling medium to the fresh air coil being functioned from full on to off under a range of pressure from 11 to 8 pounds and the diaphragm medium to the recirculated air coils being functioned from full on to off under a range of pressure of from 13 to l0 pounds. This reduces the -flow of cooling medium'through the cooling coils to the maximum extent but the by-passes 5I and 54 permit a minimum flow. Since under the outside conditions assumed, i. e. low temperature and high relative humidity, the relative humidity in the room is high, the low outlet pressure in the hygrostat outlet line holds the diaphragm valves 43 and 45 in the positions in which a relatively small amount, if any, of the water is permitted t to be pumped by the pumps 35 and39 to the inlet 50 valve 53 controlling the admission of cooling acting diaphragm valve 81 commences to open, admitting steam to the heating coils |5. This direct acting diaphragm valve 81 is operated from full oil' to on under a thermostat outlet pressure range of from 7 to 2 pounds. The heating ofthe air, of course, not only prevents the rooni'temperature from dropping below the desired minimum but also decreases the relative humidity of the air admitted so that the pressure in the hygrostat outlet line 66 rises and rst functions the diaphragm valve 45 to recirculate increasing amounts of spent water through the recirculated air coil I2 until the maximum amount is so recirculated and this coil neither cools nor dehumidies to any appreciable extent and second, to function the diaphragm valve 43 to increase the temperature of the cooling medium admitted to the fresh air coil 22. For this purpose the threeway valve 45 operates under pressures of lfrom mission and recirculation of spent cooling medium in the fresh air cooling coil 22 by the pump 33.

Under all conditions of operation before steam is admitted to the heater l the snap relay 18 is [actuated to place the dampers 15 under control of the-thermostat 60 through the reverse acting pounds.

relay 86 instead of directly. The direct acting diaphragm valve 81 does not open until the pressure in the thermostat outlet line 62 drops to 7 `Before this occurs and at 1.5 pounds pressure in the thermostat outlet line 62 the snap relay 18 is actuated so as to admit air pressure at the ful] 15 pounds in the supply line 6| to its outlet line 19 and the diaphragm of the threeway valve 8|). This pressure actuates the three-way valve 80 to disconnect its outlet line 8| from the thermostat outlet line 62 and instead connect this outlet line 8| with the outlet line 85 from the reverse acting relay 86. The reverse acting relay merely reverses the pressure in'itsloutlet lineA 85 as compared with the thermostat 'outlet line 62. At the time the snap relay operates there is no difference between the 7.5 pounds pressure in the thermostat outlet line 62 and the reverse acting outlet line 85 but as the pressure in the thermostat outlet line 62 drops in response to falling room temperature the pressure in the reverse acting relay outlet line 85 and the line 8| rises in exact proportion and this risingpressure causes the motor 16`to open the dampers 15 proportionately. At the time of operation of the snap relay 16 the dampers 15 are always closed to their maximum extent, because regardless of whether heating or cooling is being performed the load upon the apparatus during the time of change over from heating tov cooling or vice vers'a is always alike. As the temperature within the room continues to fall due to an increase in load the pressure in the thermostat outlet line drops to '1 pounds so as to open the direct acting steam valve 81 and then to continue opening this steam valve until 2 pounds is reached. When 2 pounds is reached the heating system is working under maximum load conditions and at lthis time 13 pounds of pressure is imposed upon the motor 16 and the dampers 15 are held wide open. The damper motor 16 operates under pressures of 13 to 8 pounds to move the dampers 15 from fully open to one-halt closed positions.

During winter operation the apparatus is principally employed for heating and humidifying. It is apparent that at the lower temperatures carried in the room 5 during winter operation the reverse acting hygrostat 65 serves to regulate the amount of humidification by the sprays 3 during winter operation and that the direct acting thermostat 60 serves to regulate the amount of steam admitted to the coil l5 and also the total amount of air admitted to the room by means of the dampers 15 in accordance with the heat load. When winter denitely sets in the cooling system is put out of operation in any suitable manner. This is, of course, desirable since otherwise the by-pass pipes 5| and 54 would permit the minimum amount of cooling medium to circulate through the cooling coils and also the thermostats 61 and 68 would hold the temperature of the cooling medium at its maximum temperature close tov the dewpoint of the air in the room. Such useless circulation of cooling medium through the cooling coils would merely be wasteful of refrigeration during winter operation and hence the cooling system is rendered inoperative at this season.

In order to prevent the freezing of any water in the apparatus during extremely low outside temperatures the usual preheater 2| in the fresh air duct is provided, the admission of steam from a steam line 98 being under control of a diaphragm valve 9| which is responsive to a thermostat 92 in the fresh air duct. Such a preheater is, of course, the usual expedient and forms no part of the present invention.

In the apparatus shown the entire operation from maximum cooling to maximum heating takes place under ay room temperature change of 2 to 3 and the entire operation of the air conditioning apparatus from maximum dehumidication to maximum humidiiication takesplace under a 4% change in the relative humidity in the room.

It will therefore be seen that the method and apparatus forming the subject of my vinvention provides a simple and efficient system for holding the temperature of a room within a few degrees both during winter and also during the summer and also holds a constant relative humidity within 4%. It will further be. observed that by hygrostatically controlling the temperature of the entering cooling medium and thermostatically controlling its amount' an accurate control of the temperature and relative humidity during summer operation is obtained without Waste ci refrigeration in uselessly cooling to secure the necessary dehumidication or uselessly dehumidifying to secure cooling.

I claim as my invention: v

1. The method of cooling and dehumidifying the air in an enclosure which consists in passing air and a cooling medium in heat exchanging counterflow relation, delivering the cooled air to the enclosure, maintaining the maximum initial temperature of said cooling medium at all `times at a point near the dewpoint of the air in the enclosure and regulating the minimum initial temperature of said cooling medium in response t-o the relative humidity in the enclosure.

2. The method of cooling and dehumidifying vthe air in an enclosure which consists in passing air and a cooling medium in heat exchanging counter'ow relation, delivering the cooled air to the enclosure, regulating the rate of ilow of said cooling medium in response to the dry bulb tem- Derature in the enclosure, regulating the initial temperature of the cooling medium in response to the relative humidity of the air in the enclosure and reducing the amount of cooled air delivered to the enclosure in response to a decrease in the temperature of the air in the enclosure below a point at which minimum cooling is efiected by said cooling medium.

3. In an apparatus for cooling and dehumidifying an enclosure, a multiple pass cooling coil, means for passing air through said cooling coil over the exterior of the pipes thereof and delivering the air to the enclosure, means for passing a cooling medium through the interior of the pipes of said cooling coil countercurrent to the air iiow, means for maintaining the maximum entering temperature of said cooling medium at all times at a point near the dewpoint of the air in the enclosure and means responsive to the relative humidity of the air in the enclosure fo-r regulating the minimum entering temperature of the cooling medium.

4. In an apparatus for cooling and dehumidifying an enclosure, a multiple pass cooling coil, means for passing air through said cooling coil over the exterior of the pipes thereof and delivering the air to the enclosure, means for passing a cooling medium through the interior of the pipes of said cooling coil countercurrent to the air flow, a thermostat responsive to the temperature of said cooling medium for maintaining the maximum entering tem rature of said cooling medium at all times at a point near the dewpoint of the air in the enclosure and means responsive to the relative humidity of the air in the enclosure for regulating the minimum entering temperature of the cooling medium.

5. In an apparatus for cooling and dehumidifying an enclosure, a multiple pass cooling coil, means for withdrawing air from said enclosure and passing it through said coil around the exterior of the pipes thereof, means for separately withdrawing fresh air and passing it through said coil without mixture with said enclosure air around the exterior of the pipes thereof, means for subsequently mixing the cooled fresh and cooled enclosure air and returning it to said enclosure, means for passing a cooling medium through the interior of said pipes countercurrent to the air flow, means controlling the minimum temperature of said cooling medium entering said coil in response to the relative humidity of the air within said enclosure, means controlling the rate of ow of said cooling medium through said coil in response to the dry bulb temperature of the air in said enclosure, means providing a maximum temperature of the cooling medium entering the coil at a point near the dewpoint of the air in the enclosure and means providing a minimum ratel of lflow of the cooling medium through said coil under all conditions of cooling operation.

6. In an apparatus for cooling and dehumidifying an enclosure, a multiple pass fresh air cooling coil, a multiple pass enclosure air cooling coil, means for withdrawing fresh air and passing it around the exterior of the pipes of said fresh air cooling coil, means for withdrawing air from said enclosure and passing it around the exterior of the pipes o-f said enclosure air cooling coil, means for mixing the cooled fresh and cooled enclosure air and passing it to said enclosure, means vfor passing a cooling medium through the interior of the pipes of each coil countercurrent to the air ow, means for lowering the temperature of the cooling medium entering the fresh air cooling coil in response to a rising relative humidity in said enclosure, and means for lowering the temperature of the cooling medium entering the enclosure air cooling coil in response to a further rise in the relative humidity in said enclosure.

7. In an apparatus for cooling and dehumidifying an enclosure, a multiple pass fresh air cooling coil, a multiple pass enclosure air cooling coil, means forl withdrawing fresh air and passing it around the exterior of the pipes of said fresh air cooling'coil, means for withdrawing air from said enclosure and passing it around the exterior of the pipes of said enclosure air cooling coil, means for mixing the cooled fresh and enclosure air and passing it to said enclosure, means for passing a cooling medium through the interior of the pipes of each coil countercurrent to the air ow, means for lowering the temperature of the cooling medium entering the fresh air cooling coil in response to a rising relative humidity in said enclosure, means for increasing the rate of flow of said cooling'medium through said fresh air coil in response to a rising dry bulb temperature in said enclosure, means for lowering the temperature of the cooling medium entering the enclosure air cooling coil in response to a further rise in relative humidity in said enclosure and means for increasing the rate of flow of said cooling medium through said enclosure air cooling coil in response to a further rise in dry bulb temperature in said enclosure.

8. In an apparatus for cooling and dehumidifying the air in an enclosure, a multiple pass fresh air cooling coil, a multiple passl enclosure air cooling coil, means for withdrawing fresh air and passing it through and around the exterior of the pipes of said fresh air cooling coil, means for withdrawing airi from said enclosure and passing it through and around the exterior of the pipes of said enclosure air cooling coil, means for mixing the cooled fresh and enclosure air andl passing it to said enclosure, means for passing a cooling medium through the interior of the pipes of each coil countercurrent to the air iiow, said cooling medium being supplied at a temperature below the dewpoint of the air in the enthrough said fresh air cooling coil at all times,

a valve in the cooling medium supply pipe to said enclosure air cooling coil, means operatively connecting said' last valve with said thermostat to open said last valve on a further rise in temperature in said enclosure, a cooling medium by-pass around said last valve and providing a minimum flow of cooling medium through said enclosure air cooling coil at all times, a by-pass pipe connecting the outlet of said enclosure air cooling coil with the supply pipe thereto in advance of said rst valve, a three-way valve controlling the amount of spent cooling medium returned through said by-pass pipe, means operatively connecting said three-Way valve with said hygrostat to increase the amount of cooling medium returned through said by-pass pipe in response to an initial fall in relative humidity in said enclosure, a by-pass pipe connecting the outlet of said fresh air coil with the supply pipe thereto in advance of said last fluid inlet control valve, a three-way valve controlling the amount of spent cooling medium returned through said last by-pass pipe, means operatively connecting said hygrostat with said last three-way valve to increase the amount of cooling medium returned through said last by-pass pipe'in response to a continued fall in relative humidity in said enclosure, and means responsive to the temperature of the cooling medium -entering said coils to prevent each of said three-way valves from admitting spent cooling medium through the respective by-pass pipes beyond a point at which the temperature of the cooling medium entering either coil is substantially above the dewpoint of the air in the enclosure.

9. In an apparatus for conditioning the air in an enclosure, cooling means, heating means, means for drawing air through said cooling and heating means and delivering the air into said enclosure, a dry bulb thermostat responsive to the temperature of the air in said enclosure and operating in a low temperature and high temperature range, means actuated by said thermostat during its operation in its high temperature range for rendering said heating means inoperative and regulating said cooling means in accordance with changes in the character of the air in the enclosure, said thermostat actuated means rendering said cooling means substantially inoperative when the enclosure temperature passes to the'low temperature range of said thermostat and rendering said heating means operative and under control of said thermostat in accordance with changes in enclosure air conditions, means for regulating the amount of air delivered to the enclosure, means actuated by said thermostat during one range for controlling said air regulating means in accordance with changes in the character of the air in the enclosure, and means for reversing the action o1' means for passing a cooling medium through the` inside of the pipes of both coils countercurrent to the flow of air and at an entering temperature below the dewpoint of the passing air whereby the passing air is dehumidified and cooled, means responsive to the relative humidity in the enclosure for regulating the initial temperature of the cooling medium entering said coils, means for increasing the rate of flow of the cooling me-V dium through said fresh air cooling coil in response to a rise in the dry bulb temperature in said enclosure and means for increasing the rate of flow of the cooling medium through said enclosure air cooling coil in response to a further rise in the dry bulb temperature in the enclosure.

CLAUDE A. BULKELEY. 

